Abstract: A kinetic model dC/dt=a+βC~(1/3)for suspension polymerization of vinyl chloride was developed.Kineticstudies on such polymerization were carried out in a stainless steel tube reactor in the presence of high-,medium-,or low-activity initiators at different concentrations,and at temperatures ranging from 50 to 62~C.Twenty-six sets of kinetic data were obtained under different conditions.According to these experimentalresults,the acceleration behavior of vinyl chloride polymerization was discussed in detail.It is proposed thatthe auto-acceleration effect is due to the decrease of the termination rate constnat in the polymer-rich phaseand to the increase of initiator concentration owing to volume contraction during polymerization with aninitiator of lower activity.All plots of dC/dt against C are nonlinear during the two-phase stage,while dC/dtversus C~(2/2)curves show much better linearity up to 60—70% conversion.The proposed model can beused to explain satisfactorily why the reaction order of initiators is between 0.5 and 1.0.